<%@ page language="java" pageEncoding="UTF-8" %>
<!DOCTYPE html>
<html>
<head>
    <title>Java后端WebSocket的Tomcat实现</title>
</head>
<body>
Welcome<br/><input id="text" type="text"/>
<button onclick="send()">发送消息</button>
<hr/>
<button onclick="closeWebSocket()">关闭WebSocket连接</button>
<hr/>
<div id="message"></div>
</body>

<script type="text/javascript">
    var websocket = null;
    
    function createWebSocket() {
        //判断当前浏览器是否支持WebSocket
        if (!('WebSocket' in window)) {
            alert('当前浏览器 Not support websocket')
            return;
        }

        if (websocket == null || websocket.readyState > 1) {
            websocket = null;
            var newWebsocket = new WebSocket("ws://localhost:8080//wstudy01/pchat");
            websocket = newWebsocket;
        }

        //连接发生错误的回调方法
        websocket.onerror = function () {
            setMessageInnerHTML("WebSocket连接发生错误");
        }

        //连接成功建立的回调方法
        websocket.onopen = function () {
            setMessageInnerHTML("WebSocket连接成功");
        }

        //接收到消息的回调方法
        websocket.onmessage = function (event) {
            setMessageInnerHTML(event.data);
        }

        //连接关闭的回调方法
        websocket.onclose = function () {
            setMessageInnerHTML("WebSocket连接关闭");
        }

        //监听窗口关闭事件，当窗口关闭时，主动去关闭websocket连接，防止连接还没断开就关闭窗口，server端会抛异常。
        window.onbeforeunload = function () {
            closeWebSocket();
        }
    }

    createWebSocket();

    //将消息显示在网页上
    function setMessageInnerHTML(innerHTML) {
        document.getElementById('message').innerHTML += innerHTML + '<br/>';
    }

    //关闭WebSocket连接
    function closeWebSocket() {
        websocket.close();
    }

    //发送消息
    function send() {
        var message = document.getElementById('text').value;
        //debugger

        if (!websocket || websocket.readyState > 1) { // 2 || 3
            console.log("===========未链接或链接已断开,正在建立链接中============")
            createWebSocket();
        }

        if (websocket == null) {
            alert('当前浏览器 Not support websocket')
            return;
        }

        if (websocket.readyState == 1) {
            websocket.send(message);
        } else {
            setTimeout(function () {
                console.log("等待3秒....");
                send();
            }, 3000);
        }
    }
</script>
</html>